Nanoimprint techniques have been attracting attention as micropattern-forming methods usable in semiconductor fabrication processes and processes for manufacturing magnetic recording media such as patterned media. Excellent transfer materials suitable for use in it are required.
Thermoplastic resins such as poly(methyl methacrylate) are used as transfer materials for nanoimprinting in some cases. In such cases, the following cycle is usually used: a cycle in which a coated material is heated to a temperature higher than or equal to the glass transition temperature thereof, pressed with a die, cooled, and then the die is removed. There is a problem in such a method that it takes a very long time and therefore has low throughput.
Japanese Unexamined Patent Application Publication No. 2003-100609 discloses a technique for forming a micropattern in such a manner that a coated film is formed on a substrate using a solution-processing material containing a solvent and a hydrogenated silsesquioxane which is one of siloxane compounds and is then pressed with a die at room temperature, the solvent is removed, and a hydrolytic curing is carried out. Japanese Unexamined Patent Application Publication No. 2005-277280 discloses a technique for obtaining a micropattern in such a manner that a coated film is formed on a substrate by a composition comprising a catechol derivative and a resorcinol derivative and is then pressed with a die at room temperature.
These techniques, which are called room-temperature imprinting techniques, can omit heating-cooling cycles. However, these techniques require a long time for pressing with a die and therefore have insufficient throughput. Stampers are pressed with a high pressure and therefore have a drawback in lifetime; hence, these techniques cannot be said to be sufficient as mass-production techniques as well.
A technique, called UV nanoimprinting, using a photocurable resin curable by an ultraviolet ray has been proposed. In this process, a micropattern is formed in such a manner that after the photocurable resin is coated, the resin is cured by irradiation with an ultraviolet ray while pressing the resin with a stamper, and the stamper is then removed therefrom. This process includes no heating-cooling cycle. The curing by the ultraviolet ray can be completed in a very short time. The force applied for the pressing with the stamper is small. It is likely that the process can solve the above various problems.
In UV nanoimprinting an organic resin such as an acrylic resin is usually used. In the case of using a micropattern formed therefrom as a resist, selectivity on etching rates regarding the types of etching gases is important. The term “selectivity on etching rates” as used herein means that the rate of etching varies depending on the types of etching gases. The fact that the etching rate varies significantly means that selectivity etching rates is high.
In the case where the micropattern functions as a resist, the micropattern needs to have high resistance to an etching gas and also needs to be readily removed by a gas used for the removal when removed. That is, the micropattern needs to have high selectivity on etching rates. Examples of gases often used as etching gases include fluorine-based gases and an oxygen gas. Resins generally do not have significant differences in etching rates of the fluorine-based gases and the oxygen gas. In order to increase selectivity on etching rates of fluorine-based gases and the oxygen gas, a silicon compound is usually used. The aforementioned hydrogenated silsesquioxane is an example of the silicon compound and is characteristic in that the hydrogenated silsesquioxane is etched with the fluorine-based gases at a high rate but is etched with an oxygen gas at a very low rate. However, the hydrogenated silsesquioxane is not photocurable and therefore has a problem of being applicable to UV nanoimprint process.
As a method solving the problem, Japanese Unexamined Patent Application Publication No. 2007-72374 discloses a process which uses a silicon compound synthesized by a sol-gel process and has a functional group. This technique is useful in solving the above problem. However, in this technique, the molecular weight of the silicon compound cannot be increased because the increase of the molecular weight of the silicon compound by the sol-gel process causes the compound to be gelled to become a compound insoluble in any solvent. Therefore, the process suggested in Japanese Unexamined Patent Application Publication No. 2007-72374 has a problem that it is difficult to balance the strength and flexibility of a micropattern during and after the imprint molding.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-100609
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-277280
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2007-72374